I don't find any reason why IP-ID encoding in ipv4 irregular chain, should be dependent on ECN flags.
--VERIFIER NOTES--
"This errata is invalid. Those bits need to be bound in the format and needs to be done so in the irregular chain for the inner header which does special treatment for these."

pad_len has the potential to become Inferred field, by doing this we can save one byte in compressed header and can effectively increase the compression efficiency.
--VERIFIER NOTES--
Rejected, as this is not an errata, as the 'corrected text' is in fact a change to the formal definition of the header formats.